1. Field of the Invention
This invention relates generally to field emission electron sources and more specifically to field emitter materials.
2. Description of Related Art
Nanotubes made from carbon or from the combination of carbon, boron, and nitrogen have interesting structural and electronic properties that could be useful for many applications. Utilities that have been considered include high-strength lightweight fibers, chemical filters, catalysis aids, and miniature electronic wires and devices (S. Iijima, Nature 354, 56-58, 1991). The electrical properties of carbon-containing nanotubes are predicted to vary widely as a function of tube chirality, composition, and diameter (J. W. Mintmire, B. I. Dunlap, & C. T. White, Phys. Rev. Lett. 68, 631, 1992; N. Hamada, S. Sawada & A. Oshiyama, Phys. Rev. Lett. 68, 1579, 1992). Because some multi-wall nanotubes may have a complicated combination of concentric individual tubes, each with different properties, and because of the difficulty of manipulating and measuring the properties of nanoscale objects, development of carbon nanotubes for useful applications has been hampered.
A. G. Rinzler et al. (Science 269, 1550-1553, 1995) has in the past demonstrated laser-irradiation-induced electron field emission from an individual carbon nanotube. Unfortunately, for many uses of electron field emission devices it is physically cumbersome, costly, and unfeasible to use laser assisted field emission devices, such as Rinzler demonstrated. Further, the variability of emission from tube to tube makes this approach commercially unfeasible.
W. A. de Heer et al. (Chatelain, A. & Ugarte, D. Science 270, 1179-1180, 1995) have used arrays of carefully aligned carbon nanotubes to produce field emission sources. However, the difficulty of producing carefully aligned nanotubes and the fragility of the resulting structure prevents these arrays from being commercially useful.
Field emission displays (FED) are a promising challenger to the liquid crystal displays (LCD) currently used for most flat panel electronic displays. Compared to LCDs, FEDs are three times brighter, half as thick, have almost twice the viewing angle, one forth the power consumption, and more than twice the thermal operating range. But several technical barriers block use of FEDs in current flat panel displays. The barriers include: 1) maintaining the correct spacing between the field emitter tip and the cathode plate so as to maintain constant emission current on the cathode, 2) maintaining an appropriate Internal vacuum, and 3) robustness (T. Studt, Innovation spurs hardware advances, R&D Magazine, p. 14-17, April 1996).